The motors available in micro-miniature motors market have a development tendency towards DC utilization, energy saving, miniaturization and high-speed rotation. Users require the motors to be small in size and high efficiency, with motor power to be generally 100˜600 W, revolution speed to be between 8 and 25 million revolutions per minute. The bearings used in micro-miniature motors require not only to be small in size, but also to run smoothly under high revolution speed conditions, which is difficult to realize for the current bearing manufacturing.